Intermittent rotation mechanism with overload release



March 13, 1956 J. E. FEUCHT 2,737,819

INTERMITTENT ROTATION MECHANISM WITH OVERLOAD RELEASE Filed Dec. 22, 1954 INVENTOR. JACOB E. FEUCHT ATTORNEY Wttlllli United States Pat n F vanm.

Application December 22', .1954, Seriali No; 477K113 2 Claims. c1. 14-427 This, invention relates broadly to rock drills, but. more particularly to an improved rotation mechanism for rock di'illsofthe percussive type. 1 is well. known in this art rotation mechanism for 06k drills generally includes a rifle bar having a, head carrying pawls engageable with the ratchet teeth oh :1 fixed ratchet ring. The rifles. of the bar are'cooperating with. a. rifled nut-fixed within the head of an. impact delivering reciprocatory piston, so that during each. stroke of the piston in one direction. the piston is made tolrotate while the rifle har pawls are in operative engagement with the teeth of. the ratchet ring, and duringeach stroke in the other direction the rifle bar is made to? rotate while its pawl's. ride over the. teeth of the ratchet ring. This step By step rotation of the piston. is transmitted to the drill'steelj by a chuck having the shank of the drill. steel fitted therein against relative rotation the chuck beiilg connected to the piston by interengaging. splines.

Such rotation mechanism has been. found to he. satisfactory. during, normal drilling operations, butv when drillingin formation of varying density, wherein. the drill steel often becomes. stuck, that-is. embedded in the formati'on. and prevented from rotating, the, ride bar andi'i'ts cooperating nut were subjected. to excessive load which often resulted in. pawl and rifle bar. breakage. v If. no. Breakage occurred, the piston, by virtue ot'. theengagement of the. rifles of. its. nut. withthe. rifle har,, wajsfprevented from taking a full stroke and delivering impacts on. the drill steel to release it. from. its struck condition.

Itlis therefore an. object. of this inventiontoprodilce an. improved rotation. mechanism for rock drills; capable of.' automatically becoming inoperative whensubjected'to a predetermined maximum torque, thereby. eliminating. excessive wear. or breakage. of'its. operating parts. Y

Another object. of this. invention is tov provide arock drill. with arotation. mechanism: assuring complete strokes of its piston even though the drill steellbecomes or will not rotate.

Another object: of this invention is to: provide a rotation mechanism of. the ratchetv type. with resilient or cushion means" for" the rifle bar toworkagainst during normal operation andtohavean overriding efiectgshould the: use bar be subjected to aloadi greater than its designed load.

Another object of this invention is toprovide a ratchet mechanism fora rock drill piston capable ofbeco'ming 2,737,819 Patented Mar. 13,1956

2 portion of atrockdrill embodying the preferred form of the invention. I

Figure. 2 is. a cross-sectional view taken on line. 2-2 in. Figure 1.

Figure 3 is a crossrsectional. view taken on line 3--3 in Figure 1,. and

Figure 4 is a cross-sectional. view taken on line 4-4 in Figure 1..

Referring to the drawing,, 10. designates the usual. cylin? der of. a rock drill, in which is reciprocably mounted a piston 11'. The upper portion of cylinder 10 is enlarged to. form an. annular step 12 on which. rests a. valve cap 13 having. slidabl'e. therein a. valve 14 cooperating with a stationary valve block. 15 for automatically controlling supply of. pressure. fluid. alternately to the ends of cylinder10 for. eflecting. reciprocation of piston 11. in the usual and well. known. manner.

On valve. block. 151 restsv acasing. in. the form. of. an. outer ring 16, and on it a. bearing plate 1L7 whichprot'rudes. from cylinder 10 into. ahack head. 18'. The valve cap 13; valve block 15, outer ring 16 and hearing plate 1 7 are clamped between. shoulder 12 and back head 18 by two side bolts 19,. through which: the back head is also fixed .to-the..cylinder.. Valve cap- 13,, valve block 15' and outer ring 16 are locked to cylinder Ill against. rotation relativetheretohy a. locking pin or dowel. 20..

' In the usual rotation. mechanismof the rifle bar type, the outer ring L6. constitutes. a one pieceratchet ring with ratchet teeth provided on the. inner wall. thereof. In the present. construction. the ratchet: ring. takes. the form of astack of rings with every other one. including, the terminal'. ones fixed to the outer ring. 16 and the other provided inoperative under certain conditions of operation, but

capable, even when inoperative, of constantly imparting to the piston a torque below a predetermined maximum.

Another object of this invention is to produce such an improved rotation mechanism of simple and eflicient design free of movable parts such as locks, detents or the like subjected to wear and possible breakage.

Other objects of this invention not at this time more particularly enumerated will be clearly understood from the following description.

In the accompanying drawing:

Figure 1 is a partial longitudinal sectional view of a with the usual. ratchet teeth. More specifically, mounted within the outer ring. 16 is a plurality of. staked rings 21. having. their outer walls. providedwith radially extending. equally spaced lugs 22 fitting within. corresponding recesses 23, provided within the inner wall of the outer ring, thereby locking. the friction rings to the outer ring againstrelative rotation while enabling limited axial-movement of the rings between valve block 15 and. bearing plate. 17. Separating. the. non-rotating. rings 21are rotatable. ratchet rings. Slhfitted' within the outer ring, 16 for rotation relative thereto. andv having their inner walls providedv with. the usual ratchet teeth. 31.. The rings 21 and 30; are frictionalliypressed against each other by a plurality of compression. springs 32. mounted within adequate pockets 33 provided within the underside wall ofbearing plate. L7 and-actingon the upper terminal ring 21. Preferably the nonerota'table. or friction. rings 21 are made, of bronze or the like while the ratchet. rings 36 are made of steel, thereby assuring. good frictional. interenga gement off the rings and. possible rotation. of. the ratchet=rings relative to the others. without danger ofscormg.

Exceptfor thismodiliedconstruction of: the ratchet ring assembly, this rotation. mechanism: is. of. standard design and includes. the. usualI rifle bar. head 2L4. rotatahly mounted within the ratchet rings 30. Thishead carries the usual pivotally mounted pawls 2'5' urged outwardly into en.- gagement with the teeth 31' by spring biased plungers. 26'. bar head. 24. has a pilot 27. extending. upwardly therefrom and jhurnaled within bearing plate 17l From the head 24 depends a bar 28 journaled within valve block 15, and having a rifle portion 29 extending into a rifle nut, not shown, fixed within the piston head 11.

Assuming that pressure fluid controlled by valve 14 is admitted alternately into the ends of the cylinder 10 for ellecting reciprocation of piston 11, the operation of the rotation mechanism is as follows: With the helical splines or rifles of the rifle bar 28 inclined in the direction shown in Figure 1, during each down stroke of the piston, the rifle bar will tend to rotate clockwise in Figures 2 and 3,

3 which rotation is normally prevented by the operative engagement of the pawls 25 with the teeth 31 of the ratchet rings 30. During normal drilling operation, rings 30 are held frictionally stationary between the stationary rings 21, thereby causing piston 11 to rotate in a counterclockwise direction in Figures 2 and 3 or clockwise direction in Figure 1, which rotation is in turn transmitted to the drill steel in a well known manner. During the upward strokes of the piston, rotation in a counterclockwise direction in Figures 2 and 3 is imparted to the rifle bar 28, While the pawls 25 ride over the teeth 31 of the ratchet rings 30. In this instance piston 11 moves axially without rotating.

As so far explained, the operation of the improved rotation mechanism is the same as that of standard construction, and during normal operating conditions, it functions substantially in the same manner as the usual rotation mechanism of the rifle bar type.

Assuming now that instead of normal drilling operation, holes are being drilled in a formation of varying density which causes the drill steel to become stuck in relatively soft formation. Or more broadly, assuming that the drill steel instead of being free to rotate, becomes stuck in the bottom of the drilled hole and cannot be rotated in the usual manner. In such instance, during the down stroke of the piston which now is prevented from rotating, the rifle bar is subjected to counter-forces tending to rotate it in a clockwise direction in Fig ure 2. In standard construction wherein the ratchet ring is made of a single piece fixed to the cylinder, rotation of the rifle bar in the clockwise direction is not possible by engagement of the pawls with the teeth of the ratchet ring, thereby causing breakage of the pawls and sometimes breakage of the rifle bar itself. In this improved construction, the ratchet rings 30 being held only frictionally between the non-rotatable rings 21, are capable of rotating with the rifle bar 28 relative to the outer ring 16, thereby relieving the pawls for the excessive load to which they would otherwise be subjected. Furthermore, piston 11 upon rotation of the ratchet rings and consequently of the rifle bar is now capable of completing its down strokes for delivering at least light impacts on the drill steel to dislodge it from its stuck or embedded condition.

In practice the stiffness of the compression springs 32, together with the coeflicient of friction of the ratchet rings 30 relative to the brake rings 21 must be calculated to prevent rotation of the ratchet rings during normal drilling operations, but enabling their rotation when resistance to rotation of the piston reaches a predetermined maximum.

An important feature of this invention resides in the fact that the rotation mechanism is actually never released from the piston. Under certain conditions of operation it is capable of overriding or slipping while constantly subjecting the piston to a maximum torque transmitted to the drill steel to assist in dislodging it from its stuck position. In other words, the piston remains under a constant torque which may reach a maximum beyond which the rotation mechanism is caused to override for preventing breakage of its operating parts, but such override does not release the piston of a predetermined torque which assists in dislodging the drill steel from its embedded position.

The details of structure and arrangement of parts shown and described may be variously changed and modified without departing from the spirit and scope of the invention.

I claim:

1. In a rock drill, the combination of a cylinder having a piston reciprocable therein, of a rotation mechanism for said piston including a bar extending into said piston, helical means on said bar coacting with helical means within said piston, a ratchet mechanism comprising an outer sleeve fixed within said cylinder, alternately stacked friction and ratchet rings within said outer sleeve, said friction rings being axially movable and rotationally fixed relative to said sleeve, ratchet teeth on the inner walls of said ratchet rings, means exerting axial pressure on said rings for frictionally holding said ratchet rings against rotation as long as the resistance to rotation of said piston remains below a predetermined maximum, spring biased pawl means carried by said bar operatively engaging said teeth to rotationally lock said bar in one direction to said ratchet rings and thereby translate the strokes of said piston toward one end of said cylinder into its rotation by virtue of said coacting helical means, the axial pressure exerted on said rings being calculated to enable rotation of said ratchet rings and bar in said one direction when said resistance to rotation exceeds said maximum, thereby rendering said rotation mechanism inoperative.

2. In a rock drill, the combination of a cylinder having a piston reciprocable therein, of a rotation mechanism for said piston including a bar extending into said piston, helical means on said bar coacting with helical means within said piston, a ratchet mechanism comprising an outer sleeve fixed within said cylinder, alternately stacked friction and ratchet rings concentric within said outer sleeve, said friction rings being axially movable and rotationally fixed relative to said sleeve, ratchet teeth on the inner walls of said ratchet rings, spring means exerting axial pressure on said rings for frictionally holding said ratchet rings against rotation as long as the resistance to rotation of said piston remains below a predetermined maximum, spring biased pawl means pivotally carried by said bar engaging said teeth to rotationally lock said bar in one direction to said ratchet rings and thereby translate the strokes of said piston toward one end of said cylinder into its rotation by virtue of said coacting helical means, said pawl means riding over said teeth during the rotation of said bar in the other direction by virtue of said coacting helical means during the strokes of said piston toward the other end of said cylinder, the axial pressure exerted on said rings being calculated to enable rotation of said ratchet rings and bar in said one direction when said resistance to rotation exceeds said maximum, thereby allowing said bar to rotate instead of the piston during its strokes toward said one end of said cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 1,946,956 Waseige Feb. 13, 1934 2,062,085 Campbell Dec. 1, 1936 FOREIGN PATENTS 299,913 Germany Aug. 13, 1917 

